Hi
This is my first post as a newbie to batteries and chargers ; apologies if this question has been asked before
I have bought a Zanflare C4 charger and find the test function is too slow as the discharge rate is limited to 500mA which takes ages ; I also have a MiBoxer charger but this cannot discharge batteries
So my question is ; is there a piece of hardware out there that can rapidly but safely discharge AA/AAA/18650 batteries which can then be placed in a charger at 1A charge rate to get a capacity check more quickly?
Thanks
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What you want is an electronic load that can be set to a specific current or power. There are pretty cheap units like this one:
https://lygte-info.dk/review/Review%20Electronic%20load%2060W%20UK.html
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Thanks for sharing.
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Itâs a pleasure to know you, harrygee!
I grew up with a couple of kids with the last name of Gee.
I think their family was from China. 
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Hi
thanks for the info ; as a newbie it looks a bit complicated!
is there a simpler discharge device for AA/AAA/18650 batteries
that comes ready to go with a battery holder and everything included?
thanks
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Why do you need to discharge them please⌠!?
in order to charge from a completely discharged state to measure the capacity of the battery against the claimed capacity on the battery to check for reduction in performance
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I donât think you get an accurate result from testing capacity while charging
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A proper test cycle will be charge> discharge>charge, with the contained energy measurement made during the discharge phase.
Charging cells isnât 100% efficient (losses as heat, etc) so only measuring the energy put into a cell while charging will over-estimate the cell capacity.
Likely the 500ma setting youâre seeing is the testing phase, some chargers can discharge more rapidly (1A), and you will naturally see less capacity at higher outputs.
Edit to add: Welcome to BLF!
2nd edit:
Think about what youâre trying to achieve, what kind of accuracy are you looking for? Unless you spend a lot of money, or DIY something, your results may be within ~20%(?) of the true value: consumer charger-analysers are not precision instruments.
Are you going to use the test conditions the cells are rated (often described in technical data sheets) by or devise your own conditions which might better reflect your usage?
Will you test all cell chemistry and sizes the same way?
What will you do with the data once youâve collected it? There are a few threads on here where members have shown their cell spreadsheets- deeply impressive feats of organisation!
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If you want to measure capacity faster - then you need a charger capable of discharging with higher current. This is because as other members mentioned measurement happens during discharge phase of the cycle âtop up - discharge - chargeâ.
Also, consider that increasing discharge rate youâre getting lower capacity measurement. Because capacity is always rated for specific discharge current.
Otherwise I saw some loads with selectable current on Ali, make sure they have active cooling.
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Vapcel S4+ charger along with some others have capacity check function. It will full discharge the battery, then charge it and measure capacity which will be displayed on the screen once itâs done. It will not be quick though, S4+ discharges at about 240mAh rate. But itâs safe and temperature controlled, fully automatic.
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I think⌠!?
On the Vapcell S4 Plus V3.0
If you have a full charged battery you can analyze the capacity in the discharge mode in all four slots, but in the slots 1 & 4 it can do it at 1A !
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Yes thatâs what I have V3 one. In first alot to the left it was discharging 5000mAh 21700 battery at about 240mAh in auto mode.
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Welcome to the forum.
Already pointed out - charging capacity is not accurate, especially for NiMh. You want discharge capacity. The charger/discharge units work, and they are decent approximations, but usually slow. Internal Resistance readings are often pretty inaccurate. I did it that way for years-WAY better than nothing.
I finally upgraded to a decent dedicated discharge tester and am very glad I did.
I use a ZB206+ Battery Tester
and a 4 Wire Battery Resistance Capacity Test Testing Stand
This can be adjusted from 0.1A > 2.6A and is accurate and repeatable. IR readings are consistent.
Cut-off voltage can be automatic or adjusted.
You can buy similar testers with more âpowerâ if you need it.
They arenât as complicated as they first appear.
The holder can do 21700 down to AAA.
I donât use the chargers to do capacity testing anymore.
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Hi
Thanks for the reply ; this looks like just what I need!
Can you advise me of any sites to buy these?
thanks
ebay, or AliExpress. Just use the exact names for searching.
Preference?
Both sites have these, Ali being cheaper, but some folks donât like using it.
Some eBay sites clearly note it is coming from China anyway. They are ALL from China ultimately.
You will need a 12v/2A power source like the C4 has, or there is a USB powered unit, like in the review. Either is fine.
For most accuracy you also need a way to connect 2 tiny voltage wires from the 4 wire holder to the [BV +/-] port next to the power port. I do radio control planes so had some. The 2 main wires (larger) carry the current.
I found this comment to get those.
[The connector for the 4-wire measurement is a JST-XH 2.5mm 2-pin. Itâs the 2-wire version of the standard JST-XH Balance connector on every single Lithium pack. Easy to get⌠Jst Xh 2.5 2-Pin for sale | eBay HOWEVER, the standard wiring has the Pos and Neg reversed. So, remove the connectors from the shell and swap them over.]
To swap the wires there is a tiny metal tab/barb you have to push down to release the wire. Make sure the wire polarity/color is consistent with the connections on the holder and tester.
Itâs been so long that I set this up I donât recall if I had to swap the wires.
I have 2 now and use them all the time. Just got done re-testing about a half dozen 18650âs at 0.5 and 1.0A to see how they have fared over time. Some batteries certainly hold up better than others. Without a device like this it is harder to tell.
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Great info ; many thanks